He isn't weak to RuneScape gold any specific spell however, as he's wearing bulky melee armor, has a very low magic defense. Viluppo commonly drops rune items and armor as he expires, and drops his special weapons and armors (explained later). Flech can hit you using a crossbow that strikes faster and harder than Karils. It may be 100% shielded by keep from range, however, in case a bolt will of hit you, it is going to drain 1 prayer stage in the beginning.
Just to make matters all the easier for you, Flech will alter her dhide to create her invulnerable to a specific type of elemental magic (air, water, ground fire). Flech will not change dhides till she's attacked once by a different type of element (she will not alter the first time, however she will not change if she is not hit at all).
She might drop her special resistent dragonhide, and her'special' bolts. Her crossbow, however, is NOT a drop. The sword is tipped with a very powerful poison that strikes 12s consistently. She can be assaulted with any spell, however special spells like crumble undead, charge, etc.. will splash instead of hitting hard.
She will occasonally throw exploding potions in the beginning, which will hit 25 or 0. Anticipate at least one in your fight aganist her. Her armor is very lightweight, making her all the more difficult to hit.
Veneno will drop a variety of items from rune to dragon including the DRAGON SCIMITAR along with the DRAGON CHAINBODY. The chainbody is very rare, much less probable than KQ (even more than dust devils). She will also drop her powerful posion, which can just be dipped onto a dagger and buy 2007 runescape gold spear. Her sword is not a drop.